Cast Iron References

Manufacturing State of the Art Aluminum Cylinder Head Castings

Teksid Aluminum and MAGMA have established a long term relationship to achieve best quality cast components through advanced casting modeling capabilities.

In the late 1970s, Prof. Sergio Gallo, then the general manager of the Fiat foundry division, left for a business trip to the USA with a sample of an aluminum alloy cylinder head casting in his suitcase. The casting had been produced in the foundry at Carmagnola, a town 30 km south from Torino, Italy. At that time, car manufacturers were starting to think about weight reduction as an important factor for improving the fuel economy of vehicles due to oil price increases.

After proving the feasibility and cost effectiveness of mass produced aluminum alloy castings for light duty vehicle applications and the associated benefits in terms of weight reduction, cylinder head castings produced at the Carmagnola foundry began to be shipped to engine plants in the USA, soon to be followed by cylinder blocks.

After that, the aluminum division of the new company Teksid S.p.A., which originated through the combination of Fiat's iron and aluminum foundries, grew to one of the largest non-captive producer of aluminum cylinder head castings in the world in the late 1990s. In September 2002, Teksid S.p.A. sold its aluminum foundry business to a consortium of American investors. In August 2007, the Italian operation (Carmagnola plant) was reacquired by the Fiat Group while maintaining its own brand name Teksid Aluminum.

Present yearly production at the Carmagnola plant is around 19,000 tons of castings, mainly cylinder heads (over 1.5 millions parts), with a turnover of approximately 120 M€.

The relationship between Teksid and MAGMA dates back to the beginning of the 1990s, when a group of engineers at Fiat Research (CRF) started to use the, at that time new, MAGMASOFT® code for the simulation of both aluminum and iron casting processes, supported by some Teksid foundry engineers.

The encouraging results of this pioneering work convinced Teksid to bring process simulation activities in-house with the acquisition of MAGMASOFT® licenses. Within a few years, the aluminum division installed a dedicated team of engineers coordinating simulation activities across the company, defining common methodologies, performing initial simulations for prototypes, and supporting the extension of these tools to other plants, in order to allow local resources to perform the final optimization of their casting process.

In recent years, MAGMA and Teksid Aluminum have continued their cooperation by participating into two European funded projects, IDEAL (2002-20059 and NADIA (2006-2010), aimed at the development of new methodologies for the design of light alloy components, the modeling of local properties of castings, and the integration of foundry process simulation and structural analysis tools.

The challenge of new generation cylinder heads…

Today’s cylinder head castings are very challenging products: due to high specific power ratings for new engines, operating temperatures can reach or exceed 250°C at the flame deck, resulting in thermal fatigue stresses; increasing combustion pressure peaks generate severe high cycle fatigue loads (especially in diesel engines) at the bottom of the cooling water jacket.

In addition, due to the introduction of sophisticated cooling circuits, as well as new combustion and advanced valve train actuation systems, the geometry of cylinder heads is becoming more and more complex. Precise control of the metal flow into the mold and of the solidification is required to provide a sound casting with an optimal distribution of microstructure to achieve properties capable of coping with these extreme operating conditions. A fine microstructure is required in the flame deck and around the combustion chambers to provide adequate strength and ductility to withstand the high thermo-mechanical loads found in those areas. The porosity level has to be kept as low as possible to ensure proper tightness of the internal cooling circuits of the head.

… and the answers coming from simulation

The analysis of filling, solidification and potential defects using MAGMASOFT® allows the engineer to evaluate, in advance of the actual manufacture of the mold, different geometrical options such as modifications to the casting, gating and feeding systems, combinations of process parameters, and mold cooling line layout and timing. In this way, time to market of new products can be shortened and development costs cut by dramatically reducing experimental tooling and process optimization.

New micromodeling tools, further developed in the EU projects, now also allow the prediction of local structures in the casting and to estimate its mechanical properties. Heat treatment effects on residual stresses can also be taken into account and be transferred to structural analysis codes.

Calculation speed is another critical factor for the success of process simulation that has dramatically improved. The initial installation at Teksid of MAGMASOFT® on UNIX workstations in the mid 1990s required almost a week for the complete simulation of the casting process of a cylinder head. The present multi-CPU Linux cluster architecture allows the same type of simulation (but with a much finer mesh) to be completed in a matter of hours.

Shortened calculation times allow the engineers to evaluate many more design and process parameter options and opens the way for the application of automated optimization tools that, together with the experience of the foundry engineers, will help to further improve the quality of castings.